The present invention relates to a profile element in general, and more particularly to a profile element for mining application.
Still more particularly, the invention relates to a profile element for the yieldable support of mining galleries and the like.
Profile elements for yieldable support of mining galleries and the like are used in many underground applications. The profile elements are configurated as circular or arcuate elements composed of two nested-together identical members which combine the region of overlap, are so in yieldable contact with one another that when the forces exerted upon them by the overburden exceeds a certain limit, they can shift relative to one another to a limited extent, reducing the length of the arc and thus avoiding premature plastic deformation by the forces exerted from the overburden.
Two different basic types of these profile elements are known. One is described in German Pat. No. 1,010,031 and is known as the so-called "bell profile". In this profile the bottom portion is arcuately curved and merges essentially parabolically into tapering sidewalls which are terminated by outwardly directed flanges. A particular advantage of this construction is that the bottom wall is substantially reinforced in outward direction. Also, the contact area on sliding of the profile members of the profile element relative to one another is located at the sidewalls in this construction.
The second embodiment is known from German Pat. No. 1,166,121 and known as the so-called "TH-Profile". This embodiment has as an essential feature the fact that its bottom wall portion is flattened on the outer side and merges into thinner sidewalls which are also terminated by outwardly directed flanges. In this embodiment, the glide surface on shifting of the profile members relative to one another is between the flanges rather than between the sidewalls.
Both known types of profile elements have advantages. However, they also have disadvantages in that they do not meet the optimum requirements relative to the relationship of material-weight used to load supporting capability. The load supporting capability of such elements is determined in the Federal Republic of Germany and in other countries by DIN 21 538. According to this industrial standard the bending moment, which causes on bending of the profiles at a support of 1000 mm a permanent deformation of 50 to 100 mm, is determinative for the question whether or not such a profile does or does not meet the requirements of DIN 21 538.